我正在使用条件表达式示例文档中的Case method，我在SO上找到了一些答案，可以contacts或status_text订购status，在这个例子中我是使用status_text字段。我在我的api get_queryset做了所有这些，我正在做这样的事情，
def get_queryset(self):
queryset = LeadContact.objects.none()
user = self.request.user
# I have some other conditions here
# This is the conditional expressions that I'm building for order_by
case_sql = LeadContact.objects.annotate(
custom_order=Case(
When(status_text=LeadContactConstants.STATUS_CLIENT, then=Value(1)),
When(status_text=LeadContactConstants.STATUS_QUALIFIED, then=Value(2)),
When(status_text=LeadContactConstants.STATUS_CONTACTED, then=Value(3)),
When(status_text=LeadContactConstants.STATUS_PRISTINE, then=Value(4)),
output_field=CharField(),
)
).order_by('custom_order')
return queryset.extra(select={'status_text': case_sql}, order_by=['status_text'])
现在数据库正在抛出这个Traceback：
Traceback:
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
132. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/views/decorators/csrf.py" in wrapped_view
58. return view_func(*args, **kwargs)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/rest_framework/viewsets.py" in view
87. return self.dispatch(request, *args, **kwargs)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/rest_framework/views.py" in dispatch
466. response = self.handle_exception(exc)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/rest_framework/views.py" in dispatch
463. response = handler(request, *args, **kwargs)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/rest_framework/mixins.py" in list
42. page = self.paginate_queryset(queryset)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/rest_framework/generics.py" in paginate_queryset
172. return self.paginator.paginate_queryset(queryset, self.request, view=self)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/rest_framework/pagination.py" in paginate_queryset
303. return list(queryset[self.offset:self.offset + self.limit])
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/models/query.py" in __iter__
162. self._fetch_all()
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/models/query.py" in _fetch_all
965. self._result_cache = list(self.iterator())
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/models/query.py" in iterator
238. results = compiler.execute_sql()
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py" in execute_sql
840. cursor.execute(sql, params)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/backends/utils.py" in execute
79. return super(CursorDebugWrapper, self).execute(sql, params)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/backends/utils.py" in execute
64. return self.cursor.execute(sql, params)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/utils.py" in __exit__
98. six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/backends/utils.py" in execute
64. return self.cursor.execute(sql, params)
File "/home/vagrant/virtualenv/local/lib/python2.7/site-packages/django/db/backends/mysql/base.py" in execute
124. return self.cursor.execute(query, args)
File "build/bdist.linux-x86_64/egg/MySQLdb/cursors.py" in execute
205. self.errorhandler(self, exc, value)
File "build/bdist.linux-x86_64/egg/MySQLdb/connections.py" in defaulterrorhandler
36. raise errorclass, errorvalue
Exception Type: ProgrammingError at /api/sales/lead_contact/
Exception Value: (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '[<LeadContact: Liam Higgins>, <LeadContact: Juraj Polerecky>, <LeadContact: Pau' at line 1")
我正在使用这个条件的模型字段是这两个字段，就像我说我也尝试使用status但错误更不一样：
status = models.CharField(max_length=10, choices=LeadContactConstants.STATUSES, default=LeadContactConstants.STATUS_PRISTINE)
status_text = models.CharField(max_length=20, default='', blank=True)
和LeadContactConstants模型是：
class LeadContactConstants(object):
STATUS_PRISTINE = "PRISTINE"
STATUS_CONTACTED = "CONTACTED"
STATUS_QUALIFIED = "QUALIFIED"
STATUS_CLIENT = "CLIENT"
STATUSES = ((STATUS_PRISTINE, "Virgin"),
(STATUS_CONTACTED, "Contacted"),
(STATUS_QUALIFIED, "Qualified"),
(STATUS_CLIENT, "Client"))
我不知道如何处理这个，所以有人可以解释我发生了什么，我该如何解决这个问题，所以我可以正确地订购我的联系人，谢谢你。
答案 0 :(得分：2)
我不明白为什么你将其传递给.extra()。这不是它的工作原理：case_sql是查询集本身，您应该将其返回。